The Sky Tower

The Sky Tower is a building of unknown origin found during excavation of southern Kalo mounains on Dain in the year 63 BU.
Most os the the Sky Tower is located in an underground cavern deep below the ground. It was discovered during excavation of a sefia vein, which led the miners to a sealed circular chamber approximately a hundred meters wide and forty meters high. The cavern, dubbed the Sky Cavern, has large concentration of sefia in its walls, clearly associated with the anomaly in the middle.
The Sky Tower is 20 meters in diameter, and pierces the cavern at a slightly acute angle. It is mostly smooth, with only outlines of windows carved in the walls. The window openings themselves, with several exceptions, are also filled with the same stone. It is unknown how many stories high the Tower is. In fear of endangering its stability, on the outside only two additional floors were excavated below, and one above.
Upon discovery, several miners proceeded to immediately investigate the Tower. They found an opening about ten meters above ground, through which they were able to infiltrate the structure. Inside, they realized that the whole structure is upside-down, as they noticed orientation of staircases and stone ladders. This is how the anomaly got its name, the Tower that Fell From the Sky, which was soon shortened to just the Sky Tower.
The Tower interior was almost barren, with several very interesting exceptions. There are instances of the Extan language carved into the walls, which the researchers at the University of Erwy use to confirm validity of other found texts, such as the Testament to the Fall. The miners also recovered several artifacts, including the White Stone, the Beacon and a stone chest sealed by unknown means, also currently investigated by the University. The entire structure bears high resemblance to the spires of Sifi-Nor, though the reluctance of Nata-Kea to share the existence of the city with others preventes researchers from exchanging knowledge.